SPINOSAUR
US
X-FACTOR
High-spinedgiant
WHEN 97 million years ago
WHERE North Africa
n 1912 a collector for German pale
ontologist Ernst Stromer emerged
from the Egyptian desert with the
remains of the biggest predatory dinosaur
the world had ever seen. The creature
may have measured more than 50 feet
long-arguably still the largest terrestrial
carnivore known. It possessed crocodile
like teeth and a row of enormous spines
(some six feet long) projecting from the
vertebrae, which prompted Stromer to
name the beast Spinosaurus.Scientists have
argued over the function of the spines ever
Spinosaurus'svertebral projections were
connected by a fleshy membrane. Some
living lizards employ similar "sails" for
sexual display. Perhaps Spinosaurus too
sported a sail to win the attention of mates,
as some paleontologists hypothesize about
Amargasaurus (pages 32-4). The sail may
also have helped Spinosaurus regulate body
temperature, serving as a radiator to cool
the blood, much as a car radiator cools
the water circulating through an engine.
Then again, perhaps the various render
ings of a sail-bearing Spinosaurushave all
missed the mark. As Smithsonian paleontol
ogist Hans-Dieter Sues points out, other re
lated dinosaurs, such as Baryonyx, regulated
their body temperature just fine, sans sail.
Sues seconds a notion put forth a decade
ago by Jack Bowman Bailey of Western Illi
nois University: The spines instead support
ed a structure similar to a bison's hump. "If
Spinosaurushad puny, slender spines, they
How do you build a dinosaurfrom bones like these?
since. The debate offers insight into one
of the key questions paleontologists face:
How do you reconstruct a flesh-and-blood
dinosaur from just a few bones?
One way is to piece together clues by
comparing the new specimen with more
complete skeletons already in hand. Scien
tists also draw inferences from the extinct
animal's environment and the way living
creatures function with analogous skeletal
equipment. Naturally, the less one has of
a specimen, the more speculative become
the reconstructions-and the more heated
the controversy surrounding them. Over the
years, many scientists have argued that
might have supported a sail, but these were
very massive," says Sues. "It makes more
sense that Spinosaurus'sspines were embed
ded in a lot of muscle and tissue."
Other scientists argue that humps are
usually found on herbivores in arid envi
ronments, while Spinosaurus, a carnivore,
appears to have been living in a coastal
mangrove forest. Paleontologist Paul Sereno
ascribes to the theory that the spines sup
ported a sail for sexual display. Sucho
mimus, a closely related predecessor, had
much smaller vertebral spines. Millions of
years later, says Sereno, "Spinosaurustook
that trait to the extreme."
44 NATIONAL GEOGRAPHIC * DECEMBER 2007